Steam reforming of natural gas is currently the most cost effective method of producing hydrogen and carbon oxides. The gaseous mixture of hydrogen and carbon oxides (carbon monoxide and/or carbon dioxide) is hereinafter referred to as “synthetic gas” or “syngas”. Syngas is useful as an intermediate for the manufacture of products such as ammonia, methanol or synthetic petroleum. Currently, commercial methanol production is almost entirely based on reforming light hydrocarbons, especially methane, first to syngas, followed by syngas clean up, methanol synthesis, and methanol separation. This process has been the dominant route of methanol production since the 1920's. The entire process, however, is cumbersome with a high degree of complexity and associated costs. Therefore, a direct method has been developed using direct homogenous partial oxidation of methane to methanol (the “DHPO” method).
The DHPO method is however generally limited by the need to choose between high conversions and high selectivity to obtain economic yields of methanol. In both catalytic and non-catalytic DHPO methods, higher conversions tend to create the co-products hydrogen, carbon oxides, and water, whereas higher selectivity leads to lower conversion rates which has traditionally made the process uneconomic.
U.S. Pat. Nos. 8,293,186; 8,202,916; 8,193,254; 7,910,787; 7,687,669; 7,642,293; 7,879,296; 7,456,327; and 7,578,981 overcome some of the known DHPO system limitations by using a reactor quench step and a high volume recycle system with integrated separations and low pressure drop. These patents describe these DHPO system improvements in detail and are incorporated herein by reference. However, despite the improved efficiency of our DHPO process, relative and comparable to that of the syngas-based methanol synthesis, carbon oxides and hydrogen are produced in our DHPO system process. This can limit the overall carbon efficiency to less than 100%. Furthermore, to limit the buildup of such gases and nitrogen, the process requires a reject gas stream such as a purge. Said reject gas often contains some alkane content, lowering carbon efficiency.
Furthermore, the DHPO process reactor as described in our aforementioned patents and patent applications is unable to process synthesis gas. Because of this, the process excludes a wide range of carbonaceous materials from being advantageously utilized.
Accordingly, there is a need for methods and apparatuses that can produce synthesis gas from the reject gasses from the recycle loop as well as utilize synthesis gas produced gas from a variety of carbonaceous materials for enhanced carbon efficiency and process yields, as well as that can utilize the waste heat generated by the exothermic DHPO reaction